数学、解1道整式运算..

问题描述:

数学、解1道整式运算..
(2x+y)^2-4(x-y)(x+2y)
...
蛾忘记怎么解了..
thanks.|

=4x^2+y^2+4xy-4x^2-4xy+8y^2
=9y^2